LOL, T!
Well, I have a 9 year old an we spend a fair amount of time "in transit" so I TRY to vacuum it out every month. That's also about how often I zip through a car wash, too.
I find interesting stuff--hot sauce schmears, french fries, chewed gum so hard it's not sticking in the carpet, Kleenex wads to the 10th power, lollipop sticks, pencils, Sharpies, odd molded plastic thingamabobbers from somewhere deep under the seats that belong somewhere, I suppose, convenience store receipts out the wazoo, a stale cig, Squishies, an odd silly bandz, the occasional penny, dime, nickel, quarter, and recently, a teeny tiny AK-47! :)
(How's that for a run-on sentence!)